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The aim of the study was to identify the effect of composts obtained from
post-consumer wood on the dynamics of vegetative growth and greening of leaves
of canna lily (Canna x generalis L.H. Bailey) ‘Tropical Yellow’.

Two types of composts, marked OPA and OPB, were used in the research. The
composts differed in the additives of urea and macroelements at the stage of
composting. The plants were cultivated on substrate consisting of the composts
and high-moor peat in the following volumetric combinations: compost 100%,
compost 75% + peat 25%, compost 50% + peat 50%, compost 25% + peat 75%, and peat
100% (control). Each combination was used in 11 replications.

The composts from post-consumer wood differed from peat in the content of
macronutrients, pH and salinity. The composts OPA and OPB were characterised
by excessive content of nitrogen (546 and 733 mg∙dm-3), higher salinity
(297 and 430 g NaCl∙dm-3) and a low pH in H2O (pH=3.6 and pH=3.7 respectively).The
levels of macronutrients, pH and salinity of individual substrates were a derivative
of the proportion of compost and peat within the substrates.

The research included determination of the plant height, the number of leaves
and the greening index of leaves (SPAD). The analysis of the obtained results
showed that the type of substrates and its properties had a significant effect
on the vegetative growth and greening of leaves of canna lily. Higher doses of
compost (100 and 75%) in the substrates inhibited the growth of plants compared
to control plants, whereas lower doses (50 and 25%) gave results which were comparable
to control plants.

Key words:
waste, wood, composting, peat, SPAD, Canna x generalis.

INTRODUCTION

In times of growing concern for environmental protection, increasingly often
replacements for peat substrates, which are commonly used in horticulture and
imported mostly from Eastern European countries, are sought. The intense exploitation
of peat deposits in Poland, as well as in Europe, has led to considerable depletion
of peat resources and caused significant disturbances in functioning of peat
bog ecosystems. Not only are peat bogs a source of valuable organic material,
but primarily they are important ecosystems playing a significant role in water
storage, climate control and creation of living conditions for many species of
animals and plants [7]. Inappropriate management may contribute to destruction
of these hardly renewable resources. Therefore, it is necessary to introduce
other components of horticultural substrate, which will completely, or at least
partially, substitute for this natural resource. Compost is often used as a supplement
of peat in plant cultivation [6]. It is a product of microbiological aerobic
transformation of organic waste mixture [8]. Production and natural use of composts
brings a double benefit to the environment, i.e. conservation of the natural
resource that is peat and management of burdensome organic waste, such as wood
waste (including post-consumer wood). Post-consumer wood is a recyclable material
obtained from old, worn out furniture, carpentry and joinery products (doors,
windows, floors, walls) and building structures (joists, roof trusses). This
heterogeneous material consists of solid wood and composite wood materials (fibreboards,
chipboards, plywood). Due to functional aspects (appearance, extended durability)
the surface of wood products is finished with various chemical agents. Hence,
post-consumer wood, in addition to the wood itself, contains fixed synthetic
or natural additives such as paints, lacquers, wood stains, enamel paints, waxes,
glues, resins, laminates, and foils. The proportion of these additives may be
as high as 10% of the weight. The remaining 90% is biodegradable organic matter,
mainly lignocellulose.

Every year the environmental protection regulations limit the possibilities
of depositing organic waste at storage yards. This waste should be used for energy
or raw material purposes. The waste hierarchy of utilisation of all types of
waste places material use before use for energy purposes. One way of material
use of post-consumer wood is its aerobic biological utilisation in the process
of composting, which is preferred in the case of wood waste due to the high content
of lignin in wood (~25%) [8].

According to the literature, composts of various origins, for instance from
industrial, municipal, wood and other waste, may be successfully used for cultivation
of ornamental plants [4, 17, 22]. These composts are a valuable source of organic
fertilizers and minerals that are missing in barren soils [11, 12]. Composts
from post-consumer and industrial wood waste are usually characterised by overabundance
of nitrogen and deficiency of other nutritional elements compared to commercial
horticultural substrate [19, 20, 21]. Due to the diverse requirements of different
plants in terms of soil and fertilizers, it is recommended that the usefulness
of composts for cultivation of particular species be checked by means of individual
tests [5, 10, 19, 20, 21].

The aim of the present study was to determine the effect of composts obtained
from post-consumer wood on the dynamics of vegetative growth and greening of
leaves of canna lily (Canna x generalis L.H. Bailey) ‘Tropical
Yellow’.

MATERIALS AND METHODS

The experiment, aimed at determination of the usefulness of composts prepared
from wood waste in the Wood Technology Institute, was carried out in a greenhouse
of the Department of Ornamental Plants of Poznan University of Life Sciences.
The test object was canna lily (Canna x generalis L.H. Bailey) ‘Tropical
Yellow’, reproduced generatively and characterised by green leaves and
yellow flowers.

Seedlings with two or three leaves were planted on the third day of April
2012 into pots of a diameter of 17 cm and a capacity of 2100 cm3. Two types of
composts, marked OPA and OPB, were used in the experiment. These composts differed
in the additives of urea and macroelements at the stage of composting in the
form of heaps. Both composts contained post-consumer wood waste (OP) (70% dry
matter) mixed with dust waste from processing of MDF boards (6% dry matter),
mature compost from fibreboard waste (19% dry matter), high-moor peat (4% dry
matter), water (60%), and the biological inoculum Activit Las. Additionally,
the OPA variant contained 30 kg of urea per heap of a volume of ~5m3, and the
OPB variant contained 1.5 kg of ammonium nitrate, 0.4 kg of magnesium sulphate,
0.8 kg of potassium phosphate, and 0.9 kg of calcium phosphate per heap of the
same volume.

The plants were cultivated on substrates composed of peat with a supplement
of composts in different volumetric proportions. The control was a group of plants
growing on high-moor peat limed to pH in H2O = 6.3. No mineral fertilizer was
used in the cultivation of canna lily. The individual combinations are presented
below:

The experiment consisted of 9 combinations, with 11 replications, one plant
constituting a replication.

Every two weeks during the cultivation period the plant height was measured,
the number of leaves counted, and the index of leaf greening (SPAD) was determined
using the N-Tester apparatus by Yara. This measurement enables determination
of the intensity of the green colour of leaves and consists in calculation of
the quotient of light absorption connected with the presence of chlorophyll at
a wavelength of 650 nm and absorption by the leaf tissue at a wavelength of 940
nm [13].

The obtained results were statistically processed using one–way analysis
of variance, and the means were grouped using the Duncan test at a significance
level of α = 0.05.

Prior to the start of cultivation the content of macronutrients (N-NO3, P,
K, Ca, Mg, Cl), salinity and pH in H2O, as well as volumetric weight, were determined
for the substrate (Tab. 1).

Composting is a method that enables utilisation of many different, seemingly
useless, types of waste [3, 4, 8, 14]. Depending on the origin, composts may
contain very different, often high quantities of mineral salts. Therefore, in
order to minimise the negative effect of the compost itself, it is most often
used in mixtures with high-moor peat or mineral soil [6, 19, 20, 21]. Too high
doses of composts may lead to an increase in salinity and to inhibition of plant
growth due to unfavourable properties of substrate. This is confirmed by chemical
analyses, carried out as part of the authors’ own research, which showed
that the tested composts contained more nitrogen and potassium, but less calcium,
phosphorus, magnesium and chlorides. Moreover, the composts OPA and OPB were
characterised by higher salinity (297 and 430 g NaCl∙dm-3) and a low pH
in H2O (pH = 3.6 and pH = 3.7 respectively). The content of macronutrients, as
well as pH and salinity, characterising a particular substrate was a derivative
of the proportion of compost and peat (Tab. 1). The composition of the substrate
was reflected by the dynamics of plant growth, the number of leaves and their
greening level.

Monitoring of the growth dynamics, irrespective of the compost type, indicated
that the higher was the proportion of compost in the substrate, the shorter were
the plants (Fig. 3 and 4), whereas the analysis of the last measurement indicated
that, compared to control plants, the plants growing on the OPA and OPB composts
alone, and on the substrates containing 75% additives of composts, were shorter
by, respectively, 61, 43, and 35%. A similar trend was observed during the cultivation
period (Tab. 2 and 3, Fig. 1 and 2). According to Wraga [18], an increasing proportion
of compost, which is made from vegetable waste, in the substrates has an adverse
influence on the height of the star cluster (Pentas lanceolata). The negative
influence of a high dose of compost results primarily from the excessive content
of mineral salts and deteriorating physical properties of the substrates [16].
This is confirmed by the results of the analysis of substrate carried out as
part of the authors’ own experiment. In the case of compost OPA the content
of nitrogen was 546 mg∙dm-3, and in the case of compost OPB it was 733
mg∙dm-3. The high content of nitrate ions caused in salinity of peat-free
composts (Tab. 1). Salinity above the tolerance level has a negative effect on
plant growth because it reduces the osmotic potential. This applies especially
to young plants and those that are very sensitive to this parameter of the substrate.
The tolerance of plants to salinity depends on the species and variety. Very
sensitive ornamental plants such as geranium and chrysanthemum show damage at
EC 0.8–1.0 mS∙cm-1, and slightly sensitive such as amaryllis and sansevieria
tolerate salinity up to 1.4 mS∙cm-1 [2, 15]. The plants grown on the substrate
with 25% compost, irrespective of the compost type (OPA or OPB), did not
differ significantly from the plants grown on peat (Tab. 2 and 3, Fig. 5). According
to Wróblewska et al. [20], a 25% admixture of composts OPA and OPB to
mineral soil stimulated the growth of willow shoots (Salix alba). A positive
influence of a small amount of additives of compost on the plant height was also
observed by Klock-Moore [9].

Table 2. The effect of
wood waste compost OPA on the growth of canna lily

Medium

Term of measurement

15.05

30.05

15.06

30.06

Height of plants [cm]

control-peat

25.4 c*

29.6 d

31.8 c

33.1 d

100% compost

11.3 a

14.1 a

18.6 a

13.0 a

75% compost+ 25% peat

15.6 a

18.3 b

20.2 a

21.4 b

50% compost + 50% peat

20.1 b

23.5 c

26.4 b

27.2 c

25% compost + 75% peat

24.8 c

28.1 d

31.3 c

31.3 d

Number of leaves

control-peat

5.0 b

6.2 bc

7.2 c

7.6 c

100% compost

4.3 a

5.0 a

5.0 a

5.0 a

75% compost+ 25% peat

5.9 c

6.0 b

6.3 b

6.4 b

50% compost + 50% peat

5.0 b

5.9 b

6.6 b

6.8 b

25% compost + 75% peat

6.0 c

6.6 c

7.4 c

7.6 c

Greening index of leaves (SPAD)

control-peat

41.9 b

52.2 b

57.9 c

56.9 d

100% compost

21.9 a

24.4 a

27.5 a

18.8 a

75% compost+ 25% peat

30.3 a

39.8 a

47.0 b

29.6 b

50% compost + 50% peat

50.0 c

53.5 b

59.5 c

49.3 c

25% compost + 75% peat

49.6 bc

50.1 b

61.8 c

50.3 c

*means followed by
the same letter, in columns,
for each parameter separately do not differ significantly at α=0.05

Table 3. The effect of
wood waste compost OPB on the growth of canna lily

Medium

Term of
measurement

15.05

30.05

15.06

30.06

Height of plants [cm]

control-peat

25.4 c*

29.0 c

31.8 c

33.1 d

100% compost

16.2 a

17.3 a

18.1 a

19.0 a

75% compost+ 25% peat

16.4 a

17.2 a

19.7 a

21.5 b

50% compost + 50% peat

20.1 b

23.0 b

25.9 b

27.2 c

25% compost + 75% peat

26.5 c

28.2 c

30.8 c

31.3 d

Number of
leaves

control-peat

5.0 a

6.2 b

7.2 bc

7.6 c

100% compost

5.2 a

5.4 a

5.9 a

5.8 a

75% compost+ 25% peat

6.2 b

6.4 ab

7.0 bc

6.4 b

50% compost + 50% peat

6.4 b

7.0 bc

7.9 c

7.1 c

25% compost + 75% peat

6.6 b

7.6 c

7.9 c

7.4 c

Greening
index of leaves (SPAD)

control-peat

41.9 b

52.2 c

57.9 c

55.9 b

100% compost

28.0 a

22.7 a

24.1 a

16.1 a

75% compost+ 25% peat

40.0 b

37.2 b

39.8 b

21.1 a

50% compost + 50% peat

54.4 c

53.8 c

59.5 cd

56.5 b

25% compost + 75% peat

54.7 c

59.2 d

63.0 d

54.5 b

*means
followed by the same letter, in columns, for each parameter separately do not
differ significantly at α=0.05

One of the factors that decide the quality of plants is the colour of leaves,
which may be determined based on the greening index (SPAD). In the authors’ own
experiment, in the case of plants grown on substrates consisting of pure compost
and substrates containing 75% compost, the obtained leaves were characterised
by significantly lower values of SPAD compared to control plants. Moreover, chlorosis
was visible on the leaves (Fig. 3 and 4). In the case of plant cultivation on
substrates containing 50 and 25% compost, the values of SPAD were not significantly
different or were higher when compared with plants grown on peat (Tab. 2 and
3). The probable cause of the weak intensity of the leaf green colour and the
low levels of other biometric parameters could be the strongly acidic (pH < 5)
substrates containing higher doses of composts (100%, 75%) (Tab. 1). Reaction
of the soil affects plant growth and development as it regulates the absorption
of nutrients. For most plants grown in pots (containers) optimum pH of the soil
is 6.0–6.5 (slightly acid) [2, 15].

Fig. 3. Quality of canna lily plants grown in the substrates containing OPA compost and in the peat (Torf)

Fig. 4. Quality of canna lily plants grown in the substrates
containing OPA compost and in the peat (Torf)

The statistical analysis showed that the plants cultivated on compost alone
produced fewer leaves compared to the rest of the plants (Tab. 2 and 3).

The conducted tests proved that composts obtained from post-consumer wood
may be used in a mixture with peat, in an amount of compost not exceeding 50%,
for the cultivation of canna lily. The authors think that in the cultivation
of Canna x generalis could be used higher doses of composts from
post-consumer wood waste provided that they are limed to slightly acid pH.

CONCLUSIONS

The type of substrates had a significant effect on the vegetative growth
and greening of leaves of canna lily (Canna x generalis L.H. Bailey) ‘Tropical
Yellow’.

Our results show that the higher doses of compost (100 and 75%) in the substrates
inhibited the growth of plants.

Lower doses of compost (50 and 25%) gave results which were
comparable to control plants.

The scientific work was financed by funds for science in the years 2010–2013
as a part of research project no. NN309281637.

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